Observer's guide
About de Mairan's Nebula
de Mairan's Nebula (M43) is catalogued as a diffuse nebula in Orion. Its J2000 position is RA 05:35:31.38, Dec -05:16:02.9, corresponding to 83.8792 degrees RA and -5.27 degrees Dec. The local catalogue places it about 1,600 light-years away. Its referenced angular extent is approximately 20 by 15 arcminutes.
Observing tips
StarWatchr rates this as an easy target at magnitude 9. It is associated with winter observing, with midnight placement typically strongest around December. From 52 degrees north its theoretical meridian altitude is about 32.7 degrees; local horizons and the live altitude chart determine the practical window.
Because it is faint, use a larger aperture where possible, avoid bright Moon conditions, and use averted vision.
What to expect
The SIMBAD classification for the matched source is HII. The SIMBAD record currently connects it to 204 bibliographic references.
Its roughly 20 arcminute span suits a medium field of view. Use the listed 20 by 15 arcminute extent to check framing, and treat catalogue magnitude as integrated brightness rather than a direct measure of visual contrast.